A press machines such as a transfer press that conducts a plurality of steps in press-processing is provided with a workpiece transfer device that sequentially transfers a workpiece to a subsequent step. The workpiece transfer device includes a pair of bars disposed along a workpiece transfer direction, the pair of bars each having a workpiece holder for holding the workpiece. The pair of bars are moved in feed, lift and clamp directions to transfer the workpiece.
In the press machines, when a die is changed, the workpiece holder and the bars need to be replaced. Accordingly, each of the bars of a related-art workpiece transfer device is constituted by a portion fixed to the press machine and a portion for holding the workpiece holder, the two portions being separable from each other (see, for instance, Patent Document 1). In the workpiece transfer device disclosed in Patent Document 1, a first bar and a second bar of the bars are connected to each other and separated from each other by a connecting device.
The connecting device includes: a wedge-shaped member provided on the first bar; and an engaging claw provided on the second bar and engageable with the wedge-shaped member. The wedge-shaped member is provided on an end of a piston. When the piston is moved by air pressure, the wedge-shaped member protrudes toward the second bar to engage with the engaging claw, so that the first bar is connected with the second bar. To release the connection, a disconnecting device that is provided as a separate component from the connecting device opens the engaging claw to release the engagement of the wedge-shaped member.
[Patent Document 1] Japanese Utility Model Registration No. 2583175 (Pages 5 to 7, FIG. 1)